Boron USB Inoperative with BAT only Supply?


Will the USB port operate on the nrF52840 if the Boron is powered through the BAT pin only? I’m using a data-only USB cable (i snipped the red VCC wire of a standard Particle supplied cable) to read the output of the USB port, but I’m not getting any responses when the Boron is powered via BAT pin and working normally (I can see the output in the Particle Console from my webhooks). Looking at the schematic it appears that VBUS_NRF might need power to power the USB port. Is that correct?


While the data-only cable works great on Gen 2, it does not work on Gen 3. The reason is that the nRF52 has the USB power pin connected to the nRF52840 VBUS. The MCU uses this to know if USB is connected, and if not, it powers down the USB block in the MCU, which is why USB stops working.

To capture logs off a Gen 3 device while, for example, taking power measurements, I use a FT232 USB-to-serial converter connected to TX. The one I have from SparkFun can be powered by its USB, so I just connect TX, RX, and GND to the Boron.

Rats! But it makes sense. I will look into the solution you suggest. Thanks for your help!

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